JAVA 객체지향

디자인패턴

2018.09.04

Chapter 14 컴퍼지트 패턴

1. 컴퓨터에 추가 장치 지원하기

Computer

- Keyboard

- Body

- Monitor

1. 컴퓨터에 추가 장치 지원하기

public class Keyboard {
    private int price;
    private int power;

    public Keyboard(int power, int price) {
        this.power = power;
        this.price = price;
    }

    public int getPrice() {
        return price;
    }

    public int getPower() {
        return power;
    }
}

1. 컴퓨터에 추가 장치 지원하기

public class Computer {
    private Body body;
    private Keyboard keyboard;
    private Monitor monitor;
    
    public void addBody(Body body) {
        this.body = body;
    }

    public void addKeyboard(Keyboard keyboard) {
        this.keyboard = keyboard;
    }

    public void addMonitor(Monitor monitor) {
        this.monitor = monitor;
    }

    public int getPrice() {
        int bodyPrice = body.getPrice();
        int keyboardPrice = keyboard.getPrice();
        int monitorPrice = monitor.getPrice();
        return bodyPrice + keyboardPrice + monitorPrice;
    }

    public int getPower() {
        int bodyPower = body.getPower();
        int keyboardPower = keyboard.getPower();
        int monitorPower = monitor.getPower();
        return bodyPower + keyboardPower + monitorPower;
    }
}

2. 문제점

Computer

- Keyboard

- Body

- Monitor

추가해줘

- Speaker

- Mouse

2. 문제점

public class Speaker {
    private int price;
    private int power;

    // 생략
}

- Speaker class 추가

2. 문제점

- Computer class 수정

public class Computer {
    private Body body;
    private Keyboard keyboard;
    private Monitor monitor;
    private Speaker speaker; // 추가
    
     // add 함수 생략
        
    public void addSpeaker(Speaker speaker) {
        this.speaker = speaker;
    }

    public int getPrice() {
        int bodyPrice = body.getPrice();
        int keyboardPrice = keyboard.getPrice();
        int monitorPrice = monitor.getPrice();
        int speakerPrice = speaker.getPrice();        // 추가
        return bodyPrice + keyboardPrice + monitorPrice + speakerPrice; // 수정
    }

2. 문제점

- Computer class 수정

public class Computer {
    private Body body;
    private Keyboard keyboard;
    private Monitor monitor;
    private Speaker speaker; // 추가
    
     // add 함수 생략
        
    public void addSpeaker(Speaker speaker) {
        this.speaker = speaker;
    }

    public int getPrice() {
        int bodyPrice = body.getPrice();
        int keyboardPrice = keyboard.getPrice();
        int monitorPrice = monitor.getPrice();
        int speakerPrice = speaker.getPrice();        // 추가
        return bodyPrice + keyboardPrice + monitorPrice + speakerPrice; // 수정
    }

OCP 위반

3. 해결책

public abstract class ComputerDevice {
    public abstract int getPrice();
    public abstract int getPower();
}

public class Keyboard extends ComputerDevice {
    private int price;
    private int power;
    
    public Keyboard(int power, int price) {
        this.power = power;
        this.price = price;
    }

    public int getPrice() {
        return price;
    }

    public int getPower() {
        return power;
    }
}

3. 해결책

public class Computer extends ComputerDevice {
    private List<ComputerDevice> components = new ArrayList<>();
    
    public void addComponent(ComputerDevice component) {
        components.add(component);
    }

    public void removeComponent(ComputerDevice component) {
        components.remove(component);
    }

    public int getPrice() {
        int price = 0;
        for (ComputerDevice component : components) {
            price += component.getPrice();
        }
        return price;
    }

    public int getPower() {
        int power = 0;
        for (ComputerDevice component : components) {
            power += component.getPower();
        }
        return power;
    }
}

3. 해결책

public class Client {
    public static void main(String[] args) {
        Body body = new Body(100, 70);
        Keyboard keyboard = new Keyboard(5, 2);
        Monitor monitor = new Monitor(20, 30);

        Computer computer = new Computer();
        computer.addComponent(body);
        computer.addComponent(keyboard);
        computer.addComponent(monitor);

        int computerPrice = computer.getPrice();
        int computerPower = computer.getPower();
        
    }
}

4. 컴퍼지트 패턴

부분 - 전체 관계 정의할 때 유용

Component: 구체적인 부분, Leaf, Composite 클래스의 공통 인터페이스
Leaf: 구체적인 부분 클래스, Composite 객체의 부품
Composite: 전체 클래스, 복수개의 Component 갖도록 정의